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Form N-400 Explained: What It Asks and What the Hard Words Mean
By David N. Smith, TGM, Athens, Greece
Last reviewed: October 21, 2026
Short answer: Form N-400, the Application for Naturalization, is the form a permanent resident files with USCIS to become a US citizen. It asks about your identity, addresses, family, work, travel, criminal history and loyalty to the United States. You must answer every question truthfully, use the current edition, and be ready to discuss your answers at the interview.
The N-400 is long, and the legal wording is difficult even for native English speakers. At the interview an officer will ask about what you wrote, often in different words from the form. If you do not understand a term, you may answer incorrectly, and a wrong answer can look like dishonesty. This guide explains how to prepare, walks through the form's main sections, and defines the words that most often cause confusion.
Before you start
- Confirm that you are eligible. Check the citizenship requirements. Filing too early costs a non-refundable fee.
- Use the current edition. USCIS rejects outdated editions. Download the form and instructions from the USCIS N-400 page on the day you file.
- Read the instructions fully. They list the supporting evidence for each situation.
- Collect your documents before you begin, so you can check dates and details.
- Decide whether to get legal help. This is a good idea if you have a criminal record, long trips, tax problems or an exception request.
- Learn the key terms below.
Online or paper?
- Online filing uses a USCIS account. You can save a draft, upload documents, review answers, sign electronically and pay in the same system. It costs less. See the fee guide.
- Paper filing means downloading or printing the form and mailing it to the correct USCIS lockbox. You need paper filing if you are requesting a fee waiver or reduced fee.
What the form asks: section by section
The exact part numbers change with each edition, so use these as a map, not as a checklist of numbers.
| Topic | What USCIS wants to know | Preparation tip |
|---|---|---|
| Basis for eligibility | Why you qualify (five-year rule, marriage, military) | Choose the category that matches your facts |
| About you | Full legal name, other names, birth date, A-Number, Social Security number | Your name should match your green card |
| Biographic information | Ethnicity, race, height, weight, eye and hair color | Required for identity checks |
| Residence history | Addresses, usually for the past five years | List exact dates, no gaps |
| Marital history | Current and past marriages, spouse's details | Bring marriage and divorce documents |
| Children | Names, birth dates and residence of all children | Include adult and non-resident children |
| Employment and school | Jobs and education for the past five years | Explain any gaps |
| Time outside the US | Every trip of 24 hours or more, usually for five years | Check passport stamps and records |
| Background questions | Crime, arrests, immigration violations, taxes, voting, memberships, military service | Answer honestly and get legal advice if unsure |
| Selective Service | Registration for men 18 to 25 | Check your registration status |
| Oath questions | Whether you will support the Constitution and take the oath | Be ready to explain your answers |
| Reduced fee request | Household size and income (if you request it) | Attach the required evidence |
| Interpreter and preparer | Who helped you read or complete the form | Everyone who helped must sign |
| Signature and additional information | Your sworn certification | Sign it, or the form is rejected |
Filing tips from USCIS instructions
- Your A-Number should appear at the top of every page if you file on paper.
- Answer every question. Write "N/A" if it does not apply, and "None" if the answer is zero.
- If you do not know an answer, explain why instead of guessing.
- On a paper form, do not use correction fluid or highlighters. If you make a major error, start over.
- Sign the form and keep a complete copy.
- If you move after filing, tell USCIS within 10 days using your online account or the address change form. Updating the post office is not enough.
Why honesty matters
USCIS compares your answers to other records, including earlier immigration applications, tax returns and background checks. A false or misleading statement can lead to denial, a finding that you lack good moral character, criminal charges, and even revocation of citizenship later. If a question is unclear, ask a legal-aid provider, and do not guess.
Glossary: the hard words on the N-400
These explanations are simplified, not legal definitions. They are meant to help you understand questions, not to replace advice.
A-Number (Alien Registration Number). The 9-digit number USCIS gives you, printed on your green card and many notices.
Alias. Any other name you have used, including a maiden name, nickname or spelling in another alphabet.
Allegiance. Loyalty. In the oath you promise allegiance to the United States.
Arrest, citation and conviction. An arrest is being taken into custody. A citation is an order to appear for a violation, such as a traffic ticket. A conviction is a finding of guilt or a guilty plea. The form asks about all of them. USCIS instructions generally say to disclose them even if the record was dismissed, sealed or expunged. Ask an attorney how to answer.
Attachment to the Constitution. A legal requirement that you support the basic principles of the US system of government.
Biometrics. Your fingerprints, photograph and signature, collected at a USCIS appointment for background checks.
Certificate of Naturalization. The document you receive at the oath ceremony, proving that you are a citizen.
Continuous residence. Living in the US without a break that is long enough to interrupt your residence. See the requirements.
Controlled substance. A drug regulated by law, such as heroin, cocaine or, under federal law, marijuana. State legalization does not change federal immigration law.
Crime involving moral turpitude. A legal term for offenses such as fraud or serious theft that are considered morally wrong in themselves. Whether a specific crime counts can be complicated. Ask an attorney.
Deportation or removal proceedings. A court case in which the government tries to make a person leave the country.
Good moral character. A standard of lawful, honest behavior judged over the statutory period.
Habitual drunkard, polygamy, prostitution. Examples of conduct listed in the law that can bar a finding of good moral character.
Interpreter vs. preparer. An interpreter translates for you at the interview. A preparer helps you fill out the form. Each signs a section.
Lawful permanent resident (LPR). A person who has a green card and the right to live and work permanently in the United States.
Lockbox. The USCIS facility that receives paper applications and fees.
Marital union. A real, shared married life, not just a marriage on paper. It matters for the three-year marriage route.
Naturalization. The process by which a non-citizen becomes a citizen.
Oath of Allegiance. The formal promise you make at your ceremony. Read the text and meaning.
Perjury. Lying under oath. The N-400 is signed under penalty of perjury.
Physical presence. The actual days you were inside the US.
Public assistance. Government benefits. The form may ask about benefits you received, and about fraud in obtaining them.
Receipt notice. The letter USCIS sends after it accepts your application, with your case number.
Request for Evidence (RFE). A USCIS letter asking for more documents, with a deadline.
Selective Service. The system through which men aged 18 to 25 must register in case of a future draft.
Totalitarian party. A political party that controls all aspects of life in a country and tolerates no opposition. Membership or affiliation can raise issues in the background questions.
Unlawful voting or false claim to citizenship. Registering or voting as a non-citizen, or saying you are a citizen to get a benefit. These can have severe consequences for your application.
After you file
- Online: you can see your receipt number and status in your USCIS account.
- Paper: USCIS mails a receipt notice; use the number to check status online.
- Next steps: a biometrics appointment, background checks and an interview. See the process overview and the interview guide.
Frequently asked questions
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It is the Application for Naturalization, the form permanent residents use to apply for US citizenship.
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Use the current edition, answer every question truthfully, write "N/A" when something does not apply, and keep your A-Number on every page if filing on paper. Then sign and keep a copy.
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Yes, through a USCIS online account. Requests for a fee waiver or reduced fee must be filed on paper.
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Correct small mistakes at the interview, where the officer will review your answers with you. If you discover a serious error before the interview, ask an attorney or accredited representative how to correct it.
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It asks about arrests, citations and detentions, and USCIS guidance generally says to disclose them even if they were dismissed, sealed or expunged. Get legal advice before answering if this applies to you.
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Legal-aid organizations, recognized community groups and Citizenshipworks offer free or low-cost help.
Sources and further reading
- USCIS, Form N-400, Application for Naturalization (form, instructions and current edition)
- USCIS, Learn About Citizenship
- 8 U.S.C. § 1427 and 8 U.S.C. § 1101(f): good moral character
- Citizenshipworks
This page is general information, not legal advice. Form editions and instructions change; always use the current version from USCIS. We are not affiliated with USCIS or any government agency. Last reviewed October 21, 2026.